1. Field of the Invention
The present invention relates to a shutter hold release mechanism for a single lens reflex camera for actuating shutter operation.
2. Description of the Prior Art
Various kinds of shutter releasing devices for releasing the hold of a shutter in a single lens reflex camera are known having a quick return mirror return, and have been proposed, whereby the most widely adopted of these is one which operates to directly release the hold member with the mirror driving member. Generally the shutter starts to run at the point in time at which the automatic diaphragm of the lens has been completely closed and the mirror has been entirely withdrawn into the photographing position, i.e., near the position at which the mirror driving member has been operated. Consequently in case of conventional devices it is necessary that the driving power charged in the mirror driving member have a sufficient strength to release the hold member at the position at which the operation is finished. Thus, it is necessary to provide overly large strength for mirror driving, so that the winding power is increased, while the durability of the parts is lowered, which is disadvantageous. Further, the viscosity of the oil for operating parts changes with change of the temperature so that the influence of temperature change upon the mirror driving member under the mirror driving load is large and therefore the operating speed changes. Further, the timing for releasing the hold member changes with the result that the shutter release timing becomes irregular.
One recent method to solve the above problem in a single lens reflex camera proposes that the shutter hold member release mechanism be provided separately. Namely, the hold release member is charged in operative engagement with the winding operation, the hold release mechanism is operated with a weak strength of the mirror withdrawal operation by the mirror driving mechanism during release operation and the shutter hold member is released with the moment of inertia and the large strength stored in the hold release member. Because the mechanism for carrying out this method necessitates an exclusive charge mechanism for charging the hold release mechanism the camera is more complicated in construction with the result that the cost is increased, while the timing adjustment of various driving mechanisms is complicated, which is disadvantageous.